The long-term objective of this proposal is to establish the number and types of genetic control mechanisms that are utilized by mammals in regulating the activity of specific enzymes and entire pathways. The specific aims of this project are: (1) to further elucidate the mechanisms whereby the Lv locus in mice controls the rate of synthesis of delta-aminolevulinate dehydratase (ALD); (2) to determine the effect of specific deleterious recessive mutations such as obese (ob), and diabetes (db) on the spontaneous tumor incidence in susceptible strains of mice; (3) to study gene dosage with respect to amount of protein produced in certain trisomic stocks and (4) to study other interesting biochemical mutants that are applicable to our continuing search for new gene systems controlling metabolic pathways.